In known circuits for forming a musical-tone signal in an electronic musical instrument, a musical-tone signal waveform is formed and is passed through an envelope circuit for forming a musical-tone signal having a particular envelope.
In this known type of circuit, the envelope circuit requires a large-capacity condenser and, therefore, the circuit is of an undesirable large size. Usually, therefore, the available envelope is limited to a particular range because of the necessity of limiting the capacity, so that it is impossible to form envelopes for various kinds of natural musical instruments as well as other envelopes of original design.